ST_Perimeter method

The units in which the perimeter should be computed. Defaults to the unit of the spatial reference system. The unit name must
match the UNIT_NAME column of a row in the ST_UNITS_OF_MEASURE view where UNIT_TYPE is 'LINEAR'.

The following example creates a multi-surface containing two polygons and an example unit of measure (example_unit_halfmetre).
The ST_Perimeter method finds the length of the perimeter, returning the value 88.0.